Interactive Effects of Chicken Manure, Urea Fertilizer, and Forage Crops on Soil Physical and Chemical Properties in Contrasting Terrace Systems of Semi‑Arid Sudan

Soil fertility degradation is a major constraint to sustainable forage production in semi‑arid regions, particularly in terrace systems where physical and chemical properties vary sharply. This study evaluated the interactive effects of treated and untreated chicken manure, urea fertilizer, and two forage crops— Clitoria ternatea ( C. ternatea ) and Chloris gayana ( C. gayana ) on soil properties in low‑ and high‑terrace soils in Sudan. Two field experiments were conducted during the 2020/2021 and 2021/2022 seasons using a split‑plot design. Soil texture, pH, electrical conductivity (EC), organic carbon (OC), and total nitrogen (N) were measured before sowing and after harvest. Untreated chicken manure, especially when combined with C. ternatea, produced the greatest improvements in OC, N, and EC. High‑terrace soils exhibited substantial increases in clay and silt fractions and a marked rise in OC (0.067% to 1.68%), whereas low‑terrace soils showed reductions in salinity and modest increases in pH. These results demonstrate that integrating fresh manure with legumes can rapidly improve soil quality in contrasting terrace systems. Long‑term studies incorporating crop yield and biological indicators are recommended to validate the sustainability of these practices.